US Army Corps of Engineers

BUILDING STRONG®

Tools for Assessing the Fate of Dredged Material

Speaker: Joseph Gailani

Research Hydraulic Engineer

Research Group:

Tahirih Lackey, Earl Hayter, Ray Chapman, Sung-Chan Kim, Paul Schroeder, and Jarrell Smith

Engineer Research and Development Center

October 25, 2012

BUILDING STRONG®

Motivation Data related to dredged

material fate for mgmt purposes are limited

Models and tools permit user to extrapolate to conditions for which data are not available

Provide framework within which to quantify fate, assess options and compare alternatives

BUILDING STRONG®

Motivation Increasingly complex issues related to dredged material fate

► Regulatory compliance► Environmental Resources/Risk Assessment► Site/lifecycle management► Dredged material as a resource► Engineering with Nature► Regional or multiple project management

Models are one of several tools used to address these issues (line/lines of evidence)

Models require improved process descriptions to address these issues Users need a suite of modeling tools

► Various levels of model (screening to detailed)► Address specific processes

Models and databases must be interconnected to provide efficient use and maximize benefit

BUILDING STRONG®

Objective Develop/maintain a suite of tools, models and databases

to address Corps issues related to dredged material fate and management► Develop needed process descriptions for improved

accuracy and range of applicability ► Increased interaction with other Corps models,

databases, and tools► Tiered models to address appropriate level of

accuracy/user needs► Demonstrate applicability

Decrease time required for model setup, application and interpretation through efficient user interfaces

BUILDING STRONG®

Transport Model Improvements Our understanding of sediment processes is improving

thanks to improved technologies Remote sensing Large data set storage Ability for field measurement at fine resolution Demonstrate applicability

Improved process descriptions incorporated into models Bottom boundary layer processes Model parameterization Long-term/large-scale change

All scales of models benefit from these new data and descriptions

BUILDING STRONG®

Provide deposition pattern and resuspension from placement

Manage placement sites Regulatory Compliance

(water column concentration)

► Section 103 of the MPRSA

► Section 404 (B)(1) of the Clean Water Act

Evaluate environmental resource issues

STFATEShort-Term Fate of Dredged Material

STFATE includes descent, dynamic collapse, bottom transport, and stripping phases

BUILDING STRONG®

MDFATE/ MPFATE Multiple Disposal Fate of Dredged Material

Multiple Placement Fate of Dredged Material• Cumulative resuspension

from placement operations (multiple STFATE clouds)

• Generate mound configuration from placement operations

• Address Issues related to: – Regulatory Compliance– Minimizing hazards– Optimizing operations,

long-term mgmt – Operational efficiency– Design capping operations

• Tool to optimize placement locations

MPFATE includes multiple STFATE simulations, mound building, erosion, consolidation, and avalanching

BUILDING STRONG®

STFATE/MPFATE Improvements

Complex hydrodynamics Complex bathymetries Improved settling algorithms Continuous or discrete discharge Source term to far field fate models

Multiple plumes for water quality assessment Complex bathymetry Optimization routines to maximize capacity

BUILDING STRONG®

GTRAN Sediment Pathway Model

Optimize Nearshore Placement Location to maximize benefit to Tybee Island and minimize rehandling

BUILDING STRONG®

PTM Particle Tracking Model

• A far field dredged material transport model specifically designed to simulate multiple scenarios

• Quantify DM transport and fate over large domains to assess impacts/risks

• PTM reduces computational intensity by only modeling transport of DM

• DM interactions with sediment bed treated through active layer dynamics

• Issues Addressed:– Far-field transport, deposition, and

resuspension– Time-varying sediment and constituent

concentration– Dose estimates at receptors

• Powerful post-processing tools – convert particle distribution to TSS, sedimentation, etc

Quantify erosion, deposition, and dose over large domain. Map sediment and constituent pathways, can use FATE model output as DM sources

BUILDING STRONG®

PTM Improvements

Computational efficiency for year+ simulations Improved boundary conditions New settling algorithms with parameterization Fish larvae behavior Modeling of silt curtain effects and other control systems

More complex bottom boundary conditions Improved wetting/drying transport algorithms Improved bottom boundary layer descriptions developed

by recent laboratory and field experiments

BUILDING STRONG®

Post-Placement migration and dispersion of dredged material mounds

Quantify► Hydrodynamic-driven mound

morphology change► Local deposition patterns and

thickness► Mass exiting local domain

Issues addressed: ► Dispersive/non-dispersive site► Direction/fate of material removed

from ODMDS ► Long-term management of dredged

material mounds ► Regulatory compliance and

resource issues► Dredged material mound as

resource for sediment nourishment

► Sediment rehandling

LTFATE Long Term Fate of Dredged Material

CurrentErosion/Deposition

TSS/Transport

SurgeWaves

LTFATE: Wave/current sediment erosion, transport, and deposition. Mound morphology, mixed sediment processes, 3-D hydrodynamics, contaminant transport

BUILDING STRONG®

LTFATE Improvements 3-D Large domain hydrodynamics, α- or z-grid Wave/current interactions 3-D, multiple grain size sediment bed and transport Floc/aggregate transport Parameterize transport processes using site-specific data Wetting/drying

Multi-Block capabilities for computational efficiency Improved bottom boundary layer descriptions developed

from recent laboratory and field experiments Fluid mud transport Improved nearshore/shallow water processes